Routing paths through a large network, such as, for example, the public switched network, are based on what is commonly referred to as the traffic, or logical network. For example, FIG. 1 illustrates a small portion of a large network, in which the interconnection of nodes, or switching centers (SC), 5, 10, 15 and 20 is based on the logical network, such that each SC appears to be connected directly to the other three SCs, thereby providing an appreciable number of alternate routes between each pair of SCs when a direct route, or path, is blocked. Thus, if it is assumed that communication path 7 between SCs 15 and 20 is momentarily blocked (for whatever reason), then SC 15 may route any additional traffic that it needs to send to SC 20 via an alternate route comprising SC 5 and communication paths 6 and 12. Alternatively, the additional traffic may be sent via the alternate route comprising SC 10 and communications paths 11 and 8. Accordingly, the level of interconnection in the logical network is apparently quite high. The high level of such interconnection is actually achieved by superimposing the logical network on what is commonly referred to as the facility network, the facility network being the actual physical network, as shown in FIG. 2.
It is seen from FIG. 2, that the interconnection of the SCs is not as expansive as it appears to be in FIG. 1. Specifically, the direct communication paths 9, 11 and 12 do not actually exist in the facility network. In fact, in the present illustrative example, communication path 9 is routed through SCs 20 and 15, communication path 11 is routed through SC 20, and communication path 12 is routed through SC 15. The alternate path therefore includes communication path 6 connected between SCs 5 and 15 and communication path 12 which is routed through SC 15. However, SC 15 is not aware that the routing of path 12 passes through SC 15 and, therefore, cannot take advantage of that fact in the direct routing of traffic between itself and SC 20. A similar case is apparent in connection with paths 11 and 8.
Thus, the way in which traffic is alternate routed is not always handled in the most expeditious and efficacious manner. Moreover, such routing becomes even less efficient in the instance where the individual communication paths are segments of the bandwidth of a cable, for example, an optical fiber cable. That is, communication paths 6 through 12 are assigned respective segments of the bandwidth of an optical fiber interconnecting SCs 5, 10, 15 and 20. Alternatively, such bandwidth could be the bandwidth of radio or microwave, or even a combination of those facilities, including optical fiber.